What are the internal pacemakers of the heart called?

What are the internal pacemakers of the heart called?

• A. AV node
• B. Bundle of His
• C. SA node
• D. Purkinje fibers

Answer: (C)

The internal pacemakers of the heart are referred to as the sinoatrial (SA) node. This structure is located in the right atrium and is responsible for initiating the electrical impulses that set the heart's rhythm, effectively acting as the primary pacemaker. The SA node generates electrical signals that cause the atria to contract, pushing blood into the ventricles. This function is crucial for maintaining a consistent and normal heart rate. While the other components of the cardiac conduction system—such as the atrioventricular (AV) node, Bundle of His, and Purkinje fibers—are important for conducting and coordinating the heart's electrical activity, they do not initiate the cardiac cycle. The AV node serves to slow down the electrical impulse before it reaches the ventricles, ensuring that they have adequate time to fill with blood. The Bundle of His and Purkinje fibers facilitate the rapid conduction of impulses through the ventricles, leading to coordinated contraction. However, these structures are not responsible for setting the pace of the heart; that role belongs solely to the SA node.

The internal pacemakers of the heart are referred to as the sinoatrial (SA) node. This structure is located in the right atrium and is responsible for initiating the electrical impulses that set the heart's rhythm, effectively acting as the primary pacemaker. The SA node generates electrical signals that cause the atria to contract, pushing blood into the ventricles. This function is crucial for maintaining a consistent and normal heart rate.

While the other components of the cardiac conduction system—such as the atrioventricular (AV) node, Bundle of His, and Purkinje fibers—are important for conducting and coordinating the heart's electrical activity, they do not initiate the cardiac cycle. The AV node serves to slow down the electrical impulse before it reaches the ventricles, ensuring that they have adequate time to fill with blood. The Bundle of His and Purkinje fibers facilitate the rapid conduction of impulses through the ventricles, leading to coordinated contraction. However, these structures are not responsible for setting the pace of the heart; that role belongs solely to the SA node.